HAIRDRESSERS' INCREASED CANCER RISK

Hairdressers' blood levels of certain carcinogens appear to be linked to the frequency with which they apply treatments, including hair dyes and permanent waves, according to a new study. The researchers could not confirm, however, that hairdressers' overall levels of the chemicals are higher than those of controls.

"We found that hairdressers using permanent hair dye and hair waving products seem to be exposed to carcinogenic aromatic amines," write Gabriella M. Johansson, from the Division of Occupational and Environmental Medicine at Lund University in Sweden, and colleagues in Occupational & Environmental Medicine. "Systematic screening of those products to identify the sources of exposure is indicated."

Aromatic amines, including o-, m-, and p-toluidine, are known or suspected to be carcinogenic. Exposure to aromatic amines is associated with bladder cancer, and bladder cancer rates are known to be increased among hairdressers. Toluidines are banned in the European Union, where the research was done, but previous studies have found that the chemicals are still present in at least some hair products.

The investigators recruited 295 hairdressers, 32 consumers who used permanent and/or semi-permanent hair dye on a regular basis, and 60 controls who had not used hair dye in the past year. All participants were nonsmoking women aged 18 to 55 years who lived in the Scania and Stockholm areas of Sweden.

The researchers tested the women’s blood for 8 chemicals: ortho-, meta-, and para-toluidine; 2-, 3-, and 4-ethylaniline; and 2,3- and 3,4-dimethylaniline. Among those chemicals, the International Agency for Research on Cancer has categorized ortho-toluidine (also known as o-toluidine) as a confirmed carcinogen in humans. Para-toluidine is a confirmed animal carcinogen. The rest are either suspected carcinogens or have insufficient data for classification.

The researchers tested levels as hemoglobin adducts in blood samples because they provide a relatively long-term picture of exposure (about 4 months) and because chemicals that attach to proteins such as hemoglobin are likely to also attach to DNA, potentially causing damage. The investigators note that the complex preparation of hemoglobin samples may introduce sources of error and that genetic factors may influence the metabolism of aromatic amines and thus the adduct levels. The chemicals were detected with gas chromatography–tandem mass spectrometry.

Overall levels of these chemicals did not differ significantly among the 3 groups. According to the investigators, this may have occurred because the controls' exposure from, for example, air, water, or food was unknown. Questionnaires did not identify any association in participants between blood toluidine levels and jobs or hobbies that might increase exposure, such as textile dyeing.

Within the group of hairdressers, levels of o- and m-toluidine increased significantly with the number of hair-waving treatments (P = .020) and permanent hair dyeing treatments (P = .026) they performed per week. The nontoluidine chemicals tested were found only at very low levels and were not related to hair product exposure. The investigators therefore suspect exposure to these chemicals comes from sources other than hair products. The researchers found no association between any of the chemicals and personal use of hair dyes.

The investigators directly tested 1 randomly selected "common commercial hair waving product," The product's fixative, 1 of its 3 components, contained m- and o-toluidine, in amounts suggesting that the typical user is exposed to between 21.6 and 18 ng of o-toluidine and 1.0 and 1.4 ng of m-toluidine.

Because skin absorption is a major route of exposure to toluidines, the investigators suggest that hairdressers protect themselves by avoiding skin contact. Hairdressers should wear gloves when possible and perform work that cannot be easily done while wearing gloves, such as cutting hair, before dyeing rather than after.

The project was supported by grants from the Swedish Council for Working Life and Social Research and by FAS-centre Metalund. The authors have disclosed no relevant financial relationships.

Occup Environ Med. Published online June 9, 2014. Abstract